Sports activities and competitive sports involving physically disabled persons have experienced tremendous growth in recent years. This has led to large organized competitive events, such as the Handicapped Olympics, for those physically handicapped athletes willing and able to participate. Hence, these serious athletic competitions are a source of accomplishment and well deserved pride amongst the participants.
Often, these organized competitive events require special or modified wheelchairs which are lighter, more agile and easier to manually maneuver. These competitive wheelchairs typically include lightweight wheelchair frames composed of high strength aluminum, carbon fibers or composite fiberglass. Further, these competitive chairs include a pair of front caster wheels and a pair of negative cambered rear drive wheels which add stability at high speeds by increasing the rear wheelbase.
While four-wheeled competitive wheelchairs are generally superior to conventional wheelchairs for most sport activities, especially competitive racing (sprint and distance), their capabilities are limited. For instance, in wheelchair sports requiring relatively sharp or short radius turning of the wheelchair, such as tennis, basketball, softball, rugby and football, these four-wheeled designs are somewhat cumbersome in sharp turns.
In an attempt to overcome these deficiencies, three-wheeled competition wheelchairs have been developed which are lighter in weight, capable of shorter radius turns, and provide less rolling resistance, such as the T-3.TM. by TOP END. The primary problem associated with these wheelchairs is that the wheelchair frame are often fixed frames which lack sufficient adjustability to accommodate the operator's specific needs on certain surfaces. For example, on softer surfaces, such as grass or clay, the front wheel is more difficult and laborious to maneuver. By moving the cumulative center of gravity of the wheelchair and the occupant rearward, less weight is centered over the front wheel, which eases turning. This is especially true in handicapped tennis where, depending upon the surface composition (i.e., clay, concrete, asphalt or grass), the ride, handling and speed capabilities of the wheelchair will differ depending upon the particular adjustments.
In some designs, the rear drive wheels can be moved more forward to move the cumulative center of gravity. This, however, may be problematic when the front-to-rear wheelbase distance is decreased which results in greater instability. In other designs, the position of the footrest device can be moved slightly forward and aft to accommodate the occupant's legs and feet. However, since the wheelchair frame is relatively fixed, the seat, carried atop the frame, cannot be adjusted relative the wheelchair frame for overall comfort.